Filtration technologies in the current household water purifier market generally include a microfiltration technology, an ultrafiltration technology, an ion exchange technology, an adsorption technology and a reverse osmosis (RO)/nano-filtration (NF) technology. For the RO/NF, the core component is a RO/NF membrane element. Compared with an industrial membrane element, the membrane in a household water purifier has a short flow passage. A water feeding manner for a traditional membrane element is that raw water is introduced in and concentrated water is discharged out in a direction parallel to a purified-water collection tube (a central tube). Since the flow passage is relatively short, the flowing speed in the membrane is poor in the case of equal water inlet flow, such that the membrane surface tends to produce a strong concentration polarization, and hence to be polluted, thus resulting in a low water use efficiency of the existing household water purifier.